1. Field of the Invention
The present invention relates to electrical connector strain relief mechanisms and more particularly to the use of indexing teeth for positive engagement between accessory teeth in a connector and a strain relief cable clamp employing an coupling ring with self locking engagement mechanisms.
2. Description of the Related Art
The assembly of a strain relief cable clamp or “backshell” which has a self-locking mechanism (for vibration resistance properties) and rear accessory teeth as defined in Military standard MS3155 onto an electrical connector having the same MS3155 accessory teeth can result in binding which precludes proper assembly of the backshell and connector. The backshell includes a self locking device which consists of two arch shaped spring fingers, each having a detent positioned at opposite ends of the arch. The two spring fingers are installed longitudinally and circumferenctially across from each other in a formed 360° slot on the interior surface of the coupling ring. The backshell body includes accessory teeth on its proximal end and spaced serrations with predetermined spacing on the circumferential periphery of the body located at the root of the teeth to engage the self locking devices. The coupling ring is provided with three inspection holes spaced at 120° around its periphery. The accessory teeth on the electrical connector are positioned on the shell or body opposite the connector engagement face.
When the backshell is coupled onto an electrical connector, the self-aligning movement or coupling of the two components is impeded when both sets of accessory teeth are at a peak-to-peak condition which often results in “binding”, creating a false coupled backshell and connector. This condition exists when the spring fingers detents on the self-locking devices on the backshell are locked onto the serrations without proper seating of the accessory teeth. In this condition, the approximately 0.035 to 0.04 radius on the peak of each interfacing tooth coupled with the large number of accessory teeth prevents any sliding action from occurring. The number of teeth can be from a minimum of twelve (12) to a maximum of fifty four (54). Applying torque to the backshell will not resolve the “binding” condition and the interfacing accessory teeth are not engaged or coupled. Therefore, the backshell is physically loose negating the desired vibration resistant properties which are non-existent without a complete mating interface of the accessory teeth. This condition often directly leads to finding non-compliance on the bonding and grounding requirements in complex systems such as aircraft.
It is therefore desirable to provide an arrangement to eliminate the problematic peak-to-peak condition during assembly of the strain relief cable clamp onto an electrical connector. It is further desirable to ensure that the ElectroMagnetic Interference/Radio Frequency Interference (EMI/RFI) performance of the backshell is not compromised or dependent on its assembly process onto the electrical connector. Additionally, it is desirable to allow self-locking devices on the backshell to not interfere with the coupling or engagement of the interfacing accessory teeth between backshell and electrical connector. It is still further desirable to eliminate the need for the inspection holes on the backshell coupling ring.
To better understand the embodiment of the invention disclosed herein, FIG. 1a discloses a prior art electrical connector 10 and strain relief cable clamp or backshell 12 with MS3155 accessory teeth. The backshell incorporates a coupling ring 14 having with self-locking devices 16 shown in detail in FIG. 1b. For the embodiment shown, the connector and clamp arrangements, the backshell self-locking devices consist of two arch shaped spring fingers each with a detent 18 positioned at its opposite ends. The two spring fingers are installed longitudinally and circumferentially across each other within a formed 360° slot 20 on the interior face of the coupling ring. The detents of the locking devices are received in serrations 22 on the circumference of the backshell as best seen in FIG. 1c. The serrations are spaced to receive the detents when the coupling ring slides over body 24 of the backshell during assembly. FIG. 2b shows the connector and backshell in partial engagement with the coupling ring engaging threads on the connector back body. Non-engagement of the interfacing accessory teeth 26 and 28 between the electrical connector and backshell is created by engagement of the self-locking devices in the serrations on the coupling ring of the backshell with the accessory teeth of the connector and backshell in a peak-to-peak condition as shown in detail in FIG. 2b. During coupling when accessory teeth 26 and 28 are at a peak-to-peak condition as shown ‘binding’ will likely occur, creating a condition of a false coupled electrical connector and backshell. A prior art solution to this problem is to examine the accessory teeth through an inspection hole 30 in the backshell coupling ring (as seen in FIG. 1a) and if a peak-to-peak condition is identified, rock the backshell back and forth to dislodge the interfacing accessory teeth from the peak-to-peak condition. This process might be repeated several times until the accessory teeth are fully engaged or coupled. As described, the process is laborious, tedious and failure prone.